Generally, there are a large quantity of zonal targets in a mountain land environment, for example, underground rivers that exist in the natural environment, and man-made underground petroleum pipelines, and railway and road tunnels that pass through mountains. The underground rivers are important water resources on one hand, and on the other hand, need to be avoided during construction in mountain land. Therefore, how to accurately detect and position an underground river has great significance for both our sustainable development and modernization progress. Road tunnels and railway tunnels can pass through mountains, which not only greatly shortens the road length and reduces time people spend on travel, but also saves a lot of manpower and material resources for constructing winding mountain roads and railways. Moreover, for automobiles, tunnels are much safer than winding mountain roads. However, once these man-made underground constructions in the mountain land environment become malfunctioning, it is difficult to detect the position where the malfunction occurs. Therefore, to accurately detect and position these underground zonal targets has significant influence on various aspects of people's transportation and life. Therefore, it is necessary to carry out study on detection and positioning of a zonal underground target in a mountain land environment with a relatively low false alarm rate and a relatively high recognition rate.
Certainly, contact type artificial detection is the commonest and most direct method for detecting tunnel facilities. However, this method is very time-consuming and needs a lot of manpower and material resources. Although infrared imaging is put forward as a new technology for detecting zonal underground targets and is applied to detection of shallow underground pipelines, the application of infrared imaging in detecting deeply buried zonal underground targets has not been reported home and abroad.
Soils and rocks absorb solar energy and generate heat, and the heat, in the form of infrared radiation, is detected by an infrared sensor. The heat field of the mountain mass generally includes a stable part and a variable part, where the variable part is the shallow mountain mass of which the temperature changes drastically under the effect of sunlight, and the stable part includes the mountain mass below the shallow mountain mass and an underground target buried therein. The sun cyclically heats the variable part of the mountain mass every day. Heat exchange between the stable part and the variable part inside the mountain mass and exchange of heat generated by the underground target itself and heat of the stable part finally cause a detectable temperature difference between the temperature of the mountain mass and the temperature of the buried target, and this temperature difference is the physical basis for detecting the underground target.
The temperature and energy of a zonal underground target are different from those of surrounding mountain mass media, and finally present a blurred Gaussian-like pulse mode (positive or negative) in the mountain mass after heat transmission and diffusion. However, due to the heat island effect of the ridge, the energy field at the ridge position also conforms to the blurred Gaussian-like pulse mode (positive or negative), which causes interference to the detection of the zonal underground target in mountain land.